Filter media having a porous polytetrafluoroethylene (PTFE) membrane are used in various applications, such as in intake air filters for turbines, air filters for clean rooms, and filters for household electric appliances. Patent Literature 1 discloses a filter medium including one support member and two porous PTFE membranes, the support member being held between the porous PTFE membranes. Patent Literature 2 discloses a filter medium including two support members and one porous PTFE membrane, the porous PTFE membrane being held between the support members. Patent Literature 1 also discloses a filter medium including two porous PTFE membranes and two support members, the porous PTFE membranes and the support members being alternately arranged.
In some cases, a filter medium is required to permit removal of dust from a surface of the filter medium so that the filter medium can be repeatedly used. As stated in Patent Literature 1, dust adhering to a surface of a filter medium can easily be removed when the surface of the filter medium is formed by a porous PTFE membrane.